Macromolecules are ubiquitous in modern society. In nature, biological systems are capable of synthesizing natural macromolecules with precisely defined length, sequence, and/or stereochemistry. However, precise control over macromolecular structure remains a key challenge in the abiotic synthesis of non-natural macromolecules. Conventional techniques have tried to address this problem by using complex techniques, specialized equipment, costly processes and/or low yield reactions that limit the utility, applicability, and/or scalability of the abiotic synthesis of well-defined non-natural macromolecules. Accordingly, improved methods and compositions are needed.